Arrangement for pressure-gas switch operating with closed gas circuit and with sf6 as the arc extinguishing medium



Nov. 25, 1969 E. A. FROWEIN 3,480,751.

ARRANGEMENT FOR PRESSURE-GAS SWITCH OPERATING' WITH CLOSED GAS CIRCUIT AND WITH SF AS THE ARC EXTINGUISHING MEDIUM Filed Sept. 16, 1966 Il ,l l I NVENTOR.

` E gber'l-.us Jrinus Frou/ein United States Patent O U.S. Cl. 200-148 2 Claims ABSTRACT F THE DISCLOSURE A circuit breaker of the gas blast type utilizes sulphur hexafluoride (SP6) as the gaseous arc extinguishing medium and the `gas flows in a `closed circuit rather than being exhausted to atmosphere. `Contaminated switch gases which ow from the switch chamber pass through a hollow insulator which connects the switch chamber, which is at high potential, with a collecting vessel which is at earth potential. To prevent any deterioration of the insulating capacity of the interior of the hollow insulator, the contaminated gases are passed through a plurality of concentric and longitudinally overslapping metallic tubes located inside the insulator which keep them out of Contact with the inner wall of the hollow insulator, and clean SP6 gas is also passed through the insulator between it and the concentric, overlapping tubes as well as between the tubes to further screen the inner wall of the insulator from the contaminated gases.

This invention concerns a gas-blast circuit breaker using sulphur hexafluorid-e (SP6) as arc extinguishing medium and having a closed gas cycle or circuit wherein the switch gases, on switching taking place, flow out of a switch chamber that is under voltage into a collecting vessel.

A gas-blast circuit breaker with a closed gas circuit and with SP6 as arc extinguishing medium is known, in which the switch gases flow into a collecting vessel through the hollow conductor of a lead-in, said collecting vessel being mounted on the end of the lead-in and carrying high Voltage. Prom there the gases pass via an insulated line and a compressor, back into the high pressure container of the circuit breaker, The disadvantage with this is that it is diicult to mount the collecting vessel, which takes up a considerable amount of space, and, since it is currentconductive, this leads to unmanageable dimensions of the whole switch. This disadvantage is particularly evident when it is desired to use a tank type construction. Purth-ermore, the known arrangement has the disadvantage that the products arising from the extinguishing gas and from the evaporated contact material under the effect of the electric arc are in part chemically aggressive, and attack the surface of the insulating tube, with the result that a conductive layer is produced. Again, very iine pulverulent compounds also occur, which deposit themselves on the surface of the insulating tube. Even with very slight amounts of dampness, there is hydrolysis of these compounds, with the result again that a conductive layer occurs, which leads to a breakdown of the insulation.

The object of this invention is to arrange the collecting vessel in such a way that the dimensions of the circuit breaker can be kept small, and to keep away from the insulator through which the gases flow, the injurious effeet of the switch gas with its attendant contaminating compounds. According to the invention a gas-blast circuit 3,480,751 Patented Nov. 25, 1969 breaker is provided having sulphur hexauoride as arcextinguishing medium in a closed gas circuit, and including a switching chamber which in operation is live, i.e. at high voltage, a gas collecting vessel which is earthed, an insulating member connecting the switching chamber to the said vessel for conveying the arc-extinguishing medium from the chamber to the Vessel on opening of the circuit breaker, a metal tube in and spaced from the insulating member to serve as a protective shield, a check valve between the vessel and the interior of the insulating member, and means for directing a flow of clean sulphur hexafluoride through the space between the insulating member and the protective shield whenever the circuit breaker is opened and prior to the separation of the circuit breaker contacts.

The invention will now be described with reference to the accompanying drawing, which shows an exemplary embodiment of the invention.

In the drawing, 1 designates the switch chamber which is filled with high pressure gas, and in which is located a tube-shaped blast-valve member 2 which has a ringshaped drive piston 3. The said valve member is inserted in the cylinder 4 and is held in the closed position by a sprng `5. At 6, pressurized gas, i.e. SP6, can be introduced for opening the blast valve. Between the interior abutments 2u of the blast valve member 2 there is located a bridging contact 7 consisting of resilient lamellae, the said bridging contact in this way being coupled positively with the blast valve member 2. The bridging contact 7 in the rest position ensures that there is good electrical connection between the movable contact 8 and the fixed contact 9. Both contacts 8, 9 are located inside the blast valve member 2, arranged concentrically thereto, and are of hollow construction. In the rest position the contact 8 is held in its position by a return spring 10. On opening of the contacts, after a certain lift of the blast valve member 2 from its seat 2b, the contact 8 is carried along by the latter, as soon as the left-hand interior abutment 2a impinges on the outer collar 8a of the Contact. An elbow pipe 11 is used for holding the fixed contact 9, and its flange 11a supports the switch chamber 1. It has an annular channel 12 which, in the rest position of the blast Valve member 2, is sealed from the switch chamber 1. At its other end annular channel 12 opens into the space 13 in the interior of an insulator 14. The latter forms the insulation between the voltage carrying switch chamber 1 and a casing 1S which is earthed and iilled with the SP6 gas at low pressure. Por this purpose the lower armature 14a of the insulator is flange-shaped and fixed to the connecting piece 15a1, to which the collecting vessel 16 is also iixed. The elbow pipe 11 is continued in the interior of the insulator 14 by a metallic protective tube 17. Tube 17 is concentrically surrounded by a further metallic protective tube 18, which is, however, held by means of a tubular insulating piece 19, the tube 18 also acting as a field control electrode between the voltage-carrying inner tube 17 and an outer, earthed tube Z0. The insulating piece 19 also connects the outer tube 20 with the tube 18. The tubes 17, 18, 20 overlap in the axial direction and screen i.e. protect the insulating piece 19 by excluding the contaminating, discharge gas products from contact with the inner wall surface of the tubular insulator 19. The interior wall surface of the tubular insulator 14 is thereby also protected i.e. screened from the outilowing switch gases. The insulating piece 19 has wall bores 21 through which the space 13 is connected with the annular spaces between the tubes 17, 18 and 18, 20. The outer tube 2.0` at its lower end is closed olf from the collecting vessel 16, in the rest position, by a check valve 22, which is under the influence of a weak closure spring 23.

The method of operation is as follows:

Por opening the contacts, pressurized SP6 gas is introduced at inlet 6, and acts on the drive piston 3 of the blast valve member 2, moving the latter to the left against the counter pressure of spring 5. The blast valve member 2 is lifted from its seat and permits the passage of the pressurized gas from the chamber 1 via the annular channel 12 into the space 13, putting this under pressure. In the further course of the movement of the blast valve member 2, the left-hand interior abutment 2a meetspthe outer collar 8a of the movable contact 8 and in this way entrains the contact. The contacts 8, 9 are now separated and the arc occurring between them is, in the known way,l blown with the SP6 gas and finally extinguished. The switch gases meanwhile flow through the contact 9 and reach the collecting vessel 16 via the elbow pipe 11 and v tubei17, the check valve 22 having opened. The switch gases are screened from i.e. prevented from coming into contact with, the interior wall of the insulator 14 by the fact that tube 17 projects into the insulator 14, tubes 17, 18 and 20 overlap, and the space 13 is already filled with pressurized gas in essentially pure state before the discharge gases start to ow. The overlapping of the tubes 17, 18, 20 also prevents direct impingement of the exhaust gas jet on the wall of the insulator 19. However, in order to keep the gas as pure as possible in the spaces between the tubes 17, 18, 20, the spaces are scoured with fresh SP6 gas from space 13, via the bores 21. After a period sufiicient for the extenguishing of the arc, the cylindrical space to the right of the drive piston 3 of the blast valve member 2 is vented at 6, so that the Valve member again moves into the closed position under the effect of the spring 5, and the return spring 10 re-closes contacts 8 and 9. The exhaust process thereby ceases. There is still a short ushing process, which concludes when the blast valve member 2 also shortly thereafter closes, and the space 13 drops to the low pressure via the bores 21. In the preferred embodiment shown, the power contacts 8, 9 open only for a brief period. A voltage isolator is arranged in series with the power contacts, opening before the closing of the said power contacts and taking over the isolation in the open position of the circuit breaker.

The advantage of the new arrangement consists above all in that the contaminated switch gases can be stored in the collecting vessel, which is earthed and therefore at all times accessible, until the fine, pulverulent impurities have deposited. The SP6 gas is finally returned in known manner through a filter and compressor into the high pressure chamber. Moreover, the check valve prevents the contaminated switch gases from being able to flow back into the insulator spaces after opening of the contacts.

I claim:

1. In a gas blast circuit breaker, the combination comprising means forming a high potential switch chamber, a pair of separable contacts located within said switch chamber, at least one of said contacts being tubular and stationary, means including a blast valve for introducing clean and pressurized sulphur hexafiuoride gas into said switch chamber for effecting separation of said contacts, a

4 double walled tubular outlet from said switch chamber comprising inner and outer metallic tubular members spaced from each other to define an annular channel therebetween, said inner tubular member being connected to said tubular contact member for conveying away contaminated switch gases generated by the arc produced upon separation of said switch contacts, a gas collection vessel at earth potential, a tubular insulator connecting said double walled tubular outlet to said gas collecting vessel, said inner tubular member extending into one end of said tubular insulator and being spaced from the wall thereof to establish an annular space therebetween which communicates with said annular channel defined by said inner and outer tubular members, at least one additional metallic tubular member spaced from and surrounding said inner tubular member in longitudinal overlapping relation within said tubular insulator and which extends beyond the other end of said tubular insulator to constitute an extension of said inner tubular member for conveying the switch gases into said gas collecting vessel through a non-return valve, said longitudinally overlapped metallic tubular members serving to prevent any part of said switch gases from reaching the inner wall of said tubular insulator and additionally acting as a field control means,

and means for directing said clean and pressurized sulphur hexachloride gas from the outlet side of said blast valve into and through said annular channel in said double walled tubular outlet in advance of separation of said switch contacts and which is discharged into said annular space between said tu-bular insulator and said inner tubular member.

2. A gas blast circuit breaker as defined in claim 1 and which further includes an additional hollow insulator surrounding and secured to said inner tubular member and which supports said additional tubular member, the wall of said additional hollow insulator being provided with ports for admitting said clean and pressurized sulphur hexachloride from said annular space into the interior of said additional hollow insulator member for ow through said additional tubular member.

References Cited UNITED STATES PATENTS 2,108,560 2/1938 Kesselring. 2,364,981 12/1944 Journeaux 200-l48 2,365,509 12/1944 Baker. 2,913,626 11/1959 Bislin 317--65 X 2,955,182 10/1960 Caswell et al. 3,339,046 8/1967 Giammona et al 200--148 FOREIGN PATENTS 1,160,061 12/1963 Germany.

ROBERT K. SCHAEPER, Primary Examiner R. A. VANDERHYE, Assistant Examiner Y Us. C1. X.R. 20o-148 

